1. Field of the Invention
The present invention relates to a printer-control apparatus, a printer-control method, and a printer and, more particularly, to a printer-control apparatus and a printer-control method capable of eliminating an error in specifying of the absolute position of a printing medium caused by reaction delay time of a mechanical paper detection sensor for detecting or sensing the front edge and/or the rear edge of the printing medium, and to a printer having such a printer-control apparatus.
2. Background Art
An inkjet printer as a kind of a printer performs printing on the surface of a printing medium by jetting ink from ink nozzles as a number of ink discharging ports formed in a print head while driving a carriage on which the print head is mounted in a main scan direction orthogonal to a printing medium carrying direction over the printing medium and by sequentially carrying the printing medium in a sub scan direction as the printing medium carrying direction.
To realize predetermined high printing quality in such a printing method, the absolute position, carried speed, and carried distance of a printing medium have to be accurately managed and controlled.
Consequently, in a normal inkjet printer, at the time of feeding a printing medium from a tray by a paper-supply roller and supplying it into the printer, the front and rear edges of the printing medium are detected by a paper detection sensor disposed near a paper insertion port and used as basic information for managing and controlling the absolute position and the carried distance of the printing medium.
The relative position of the printing medium specified from an accumulated carried amount of the printing medium by a printing medium carrying mechanism is recorded and managed independently of detection of the front and rear edges of the printing medium by the paper detection sensor. In particular, to adjust a marginal area in the periphery of a printing medium and to match the surface of a printing medium and a printing execution area in the case of performing marginless printing, the front and rear edges of the printing medium have to be detected by the paper detection sensor to detect and manage the absolute position of the printing medium.
Sensors which can be used as the paper detection sensor for detecting the front and rear edges of a printing medium are broadly divided into a mechanical sensor and an optical sensor.
The optical paper detection sensor has advantages such that response at the time of detection is high and reaction delay time is very short. On the contrary, it has disadvantages such that the price is high and a transparent printing medium such as an OHP sheet cannot be detected. Consequently, the ratio of employment as the paper detection sensor is low.
On the other hand, although the mechanical paper detection sensor has disadvantages such that response at the time of detection is lower and reaction delay time is relatively long as compared with the optical paper detection sensor, it has advantages such that the price is low and an arbitrary printing medium including a transparent printing medium can be detected. Consequently, the mechanical paper detection sensor is widely employed as the paper detection sensor.
However, the reaction delay time at the time of detection of the front and rear edges of a printing medium by the mechanical paper detection sensor causes an error in specifying of the absolute position of the printing medium.
In the case where the operation of detecting the front and rear edges of a printing medium is performed in a constant speed period in operation of carrying the printing medium, it is relatively easy to eliminate an error caused by the reaction delay time and accurately specify the absolute position of the printing medium by obtaining the reaction delay time of the mechanical paper detection sensor in advance.
In the case where the operation of detecting the front or rear edge of a printing medium is performed in an acceleration control period or a deceleration control period in the operation of carrying the printing medium, it is difficult to specify the carrying speed of the printing medium at the time point when the front or rear edge of the printing medium actually reaches the position of the mechanical paper detection sensor. It is therefore difficult to accurately specify the absolute position of the printing medium on the basis of detection of the front or rear edge of the printing medium.
An invention for correcting an error in specifying of the absolute position of a printing medium caused by reaction delay time of a mechanical paper detection sensor has been proposed and known. The gist of the invention is to execute approximation calculation by using a speed correction value in a reference table pre-stored in a memory. Refer to, for example, Japanese Patent Laid-Open Publication No. 10-291685.
Hitherto, it was rare that an error in specifying of the absolute position of a printing medium caused by reaction delay time of the mechanical paper detection sensor becomes a big issue. However, as the marginless printing is being spread and the technique development such as increase in printing picture quality progresses, it comes to be requested to specify the absolute position of a printing medium more accurately and to execute a control of carrying a printing medium on the basis of the absolute position at higher precision.
To address such a request, the specifying of the absolute position of a printing medium by approximate calculation is insufficient in precision.
Therefore, it is becoming a more important object to accurately specify the absolute position of a printing medium by eliminating an error caused by reaction delay time of a mechanical paper detection sensor.
Specifically, an error in specifying of the absolute position of a printing medium causes deterioration in precision of the control of carrying the printing medium. As a result, it causes deterioration in the picture quality of a printed image, particularly, deterioration in the picture quality caused by displacement of a printing execution area in a peripheral portion in a printing medium at the time of marginless printing and occurrence of ink mist. Consequently, it is strongly demanded to accurately specify the absolute position of a printing medium by eliminating an error caused by reaction delay time of a mechanical paper detection sensor.
An object of the invention is to provide a printer-control apparatus, a printer-control method, and a printer capable of eliminating an error in specifying of the absolute position of a printing medium caused by reaction delay time of a mechanical paper detection sensor for detecting the front edge and/or the rear edge of the printing medium.